Traditional studies on Mars entry, descent, and landing usually take a divide- and-conquer approach where each phase is investigated separately. This paper proposed a new computational approach to generate optimal guidance for mid-lift high-mass Mars entry and powered descent. First, optimal Mars atmospheric entry and optimal powered descent problems are respectively modeled. Second, optimal handover problem is formulated to integrate the Mars entry and powered descent phases in a collaborative optimization manner. Third, optimal guidance for Mars entry and powered descent is produced through online solving energy-optimal entry, propellant-optimal powered descent, and optimal handover problems iteratively. Finally, numerical simulations verified the collaborative work of the proposed computational guidance framework, and the results demonstrated the significant benefit of the optimal integrated guidance.